1. Field of the Invention
The present invention relates to a method of forming fine patterns of a thin film on a substrate in the process of manufacturing a semiconductor device and the like.
2. Background Art
FIGS. 1A, 1B, 1C, and 1D are diagrams showing a conventional method of forming patterns that uses a lithography technique.
As FIG. 1A shows, an oxide film 2 of a thickness of about 4 nm is formed on a semiconductor substrate 1 such as a silicon wafer. A polysilicon film 3 of a thickness of about 150 nm is formed on the oxide film 2, and an oxide film 4 of a thickness of about 200 nm is formed on the polysilicon film 3. Next, an organic anti-reflective film 6 of a thickness of about 100 nm is formed on the oxide film 4, and a resist pattern 7 of a line-and-space (hereafter referred to as L/S) of 0.16/0.16 xcexcm is formed on the anti-reflective film 6 with lithography equipment such as an excimer laser.
Next, as FIG. 1B shows, the anti-reflective film 6 is etched with the resist pattern 7 as a mask. Etching is performed using dry etching equipment so as not to change the line width of the resist pattern 7.
Furthermore, as FIG. 1C shows, the oxide film 4 is etched using oxide-film etching equipment.
Thereafter, as FIG. 1D shows, the resist pattern 7 is removed by ashing. Then, the polysilicon film 3 is etched with silicon dry etching equipment using the oxide film 4 as a hard mask.
As obviously seen in FIG. 1D, the pattern of the polysilicon film 3 formed by the above-described process is of the L/S=0.16/0.16 xcexcm, identical to the L/S of the resist pattern 7.
In this method, since a thin film pattern is fabricated using a resist pattern formed with a lithography technique (hereafter referred to as xe2x80x9clithography patternxe2x80x9d) as a mask, a pattern finer than the lithography pattern cannot be formed.
Although a slimming technique has been known as a method of narrowing the line width, since the space width is widened as the line is narrowed, the pattern pitch does not change from the resist pattern, and the pattern does not become finer.
The object of the present invention is to provide a method of forming a fine pattern without being obstructed by the limitation of a lithography technique.
First, a resist pattern is formed using a lithography technique on a film to be processed that has been deposited on a substrate. The resist pattern is subjected to etching to narrow the line width. Next, the first film to be processed underneath the resist pattern is subjected to anisotropic etching under a reduced pressure. Etching under a reduced pressure accelerates the etching rate in the vicinity of the side of the line of the pattern compared to other areas. Therefore, when difference in the etching rates is utilized, the underlying film to be processed can be exposed in the vicinity of the side of the line of the pattern, leaving the film to be processed in other areas. This etching exposes only the vicinity of the side of the line of the resist pattern of the second film to be processed underneath the first film to be processed, and forms the pattern of the first film to be processed. Next, the second film to be processed is etched using the pattern of the first film to be processed as a mask to form the pattern of the second film to be processed. The pitch of the resulting pattern of the second film to be processed becomes xc2xd the pitch of the resist pattern.
Other and further objects, features and advantages of the invention will appear more fully from the following description.